Back-side emission-type light emitting diodes are known. In such a device, an anode electrode or a cathode electrode are provided on the surface of a substrate that is capable of transmitting light, and the other of the anode electrode or the cathode electrode is provided on a surface of the light emitting layer stack.
In the back-side emission-type light emitting diode, a substrate generally serves as a current path. For this reason, the carrier concentration of the substrate may have influence on electrical characteristics of the device. In order to suppress this possible influence, a method of forming a conductive layer (to serve as a current path) on the surface of the substrate is adopted. However, light emitted from the rear surface of the substrate in such a device includes light rays having different emission areas along the substrate. One of the light ray emission area emits primarily direct light emitted from the lower side of the light emitting layer. The other light ray emission area emits indirect light reflected from the lower side of an electrode disposed on the substrate. This indirect light may be reflected by the rear surface of the substrate and is then further reflected by the electrode provided on the substrate. The indirect light also includes another indirect light which is initially emitted upward from the light emitting layer, then reflected downwardly by an electrode on the light emitting layer. This indirect reflected passes through the light emitting layer and is emitted from the lower side of the light emitting layer.
When a conductive layer is formed on the substrate, a portion of emitted light is absorbed into the conductive layer, especially indirect light which would be reflected at the rear surface of the substrate toward the electrode provided on the substrate. For this reason, the amount of emitted indirect light is greatly decreased, as compared to the amount of direct light. As a result, there may be a problem in that a large amount of light is unevenly distributed on the lower side of the light emitting layer, and a small amount of light is unevenly distributed on the lower side of the electrode provided on the substrate.